No user visible changes expected.
For brush assets, we need a way to store a reference to a brush in .blend files, so that the last active brush can be restored from the file. See #101908. It seems like a generally useful thing to have.
Adds a new DNA struct to store a "weak" asset reference, that is, a reference that can break under a number of circumstances, but should work reliably enough under normal usage. There's no way to reliably reference an asset currently, so this works on a "best effort" basis. It can break when assets are moved inside the asset library, asset libraries are unregistered from the Preferences, or a file is opened on a different machine with different Preferences, for example. It can also break currently if an asset library is renamed.
It contains:
- Information to identify the asset library the asset can be found in.
- A relative "identifier" (currently a relative path) for the asset within the asset library.
There's further code to resolve a weak reference to file paths and Blender library paths.
Part of #101908.
Co-authored-by: Bastien Montagne <bastien@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/105603
